1. Field of the Invention
Embodiments of the invention relate generally to data communications over power lines, and more particularly, to methods and apparatus for transferring data over a utility power distribution system, also referred to herein as a power grid.
2. Description of Related Art
Conventional carrier frequency systems are commonly used for data communications over high-tension utility power lines. It is desirable to utilize the existing power distribution infrastructure because it is widely interconnected with virtually every home and building, at least within the geographic reach of any given power grid. Conventional power line communications systems operate by impressing a modulated carrier signal on the wiring system. Different types of powerline communications use different frequency bands, depending on the signal transmission characteristics of the power wiring used. However, because the power distribution systems in most countries were originally intended for transmission of alternating current (AC) power at frequencies of 50 to 60 Hz, the existing infrastructure of power wire circuits has only a limited ability to carry higher frequencies. This is particularly the case within the “last mile” or final leg of the distribution system, which can present a bandwidth bottleneck. Furthermore, data communication rates can be inversely proportional to the distance between communicating devices. Thus, the signal propagation problem is a limiting factor for conventional power line communications.
Broadband over power lines (BPL) is another conventional method of power line communication that allows relatively high-speed digital data transmission over the existing power distribution infrastructure. BPL uses parts of the radio spectrum allocated to other over-the-air communication services. However, radio interference and substandard wiring are a limiting factors in the performance of BPL systems.